/Issued 4:12 PM CDT, Wednesday, July 17, 2013/
*This is a little alarming. Here’s the 15z Hop/WRF model total rainfall forecast for Tonight-ending at 4 AM Thursday. Note the corridor of purple and blue colors that’s 2-4″+ of rain over parts of Northcentral Minnesota. Various HRRR model runs do not back up what the Hop/WRF model is showing, so there is uncertainty in Tonight’s forecast. Torrential rain is certainly a threat if thunderstorms develop Tonight, and if they start to train (move over the same location) then some impressive rain totals could occur Tonight.
Today’s Weather Summary for Northeast Minnesota and Northwest Wisconsin
A cold front has settled into Northcentral Minnesota as of 3 PM. Another hot and muggy day for areas near and south of that boundary while it was quite a bit cooler north of that front. High temperatures ranged from the 70s and lower 80s in far Northern Minnesota, Iron Range and Arrowhead. Still steamy farther south where highs reached the upper 80s and low to mid 90s. Dew points were in the 60s and lower 70s Today with PWS of 1.50-1.90″ as of late Afternoon. Winds were out of the north, southwest or east Today at 10 to 20 mph. There’s been a few showers and thunderstorms at times since last night in Northern Minnesota, none of these storms have been very potent though, but they have been dropping quite a bit of rain and producing some lightning.
Forecast Discussion for Northeast Minnesota and Northwest Wisconsin
Short Term Forecast – Confidence: Medium-High.
Tonight (July 17th)
A cold front which was over the Northcentral part of Minnesota late This Afternoon may settle a bit more toward the south during the night, but it shouldn’t get very far south if it does at all. Abundant amounts of instability will be over the Northland Tonight with CAPE of 1000-2000 j/kg and Lifted Indices from -2 to -6C. The limiting factor for a more organized severe thunderstorm threat will be the generally weak mid level winds (20-30 knots) the best overall shear will be in far Northern Minnesota and Arrowhead, but these areas will be in somewhat weaker instability.
We should continue to see scattered showers and thunderstorms develop over parts of the Northland Tonight with lightning and heavy rain being the primary threats. Lows will be in the 60s and 70s with a few 50s in Northern Minnesota. Winds will be out of the south, north or east at 10 to 15 mph.
Thursday and Thursday Night (July 18th)
A warm front is forecast to be over Central or Northcentral Minnesota Tomorrow Morning. This boundary is expected to lift north during the day, but will then be replaced by a southeastward moving cold front which should push through the Northland Thursday Night.
No doubt there’s going to be plenty of fuel in the atmosphere to help generate thunderstorms this period, but there is some uncertainty of the cap strength (warm temps aloft) if this cap is strong or doesn’t break it would mean a decreased chance for convection/severe weather Tomorrow and Tomorrow Night.
The way it looks now is that there could be 2 separate rounds of thunderstorms with one during the Morning hours and the other round coming sometime late Tomorrow Afternoon/Tomorrow Night.
CAPE of 1500-3000 j/kg and Lifted Indices of -4 to -8C are expected over the Northland with a 30-45 knot SW low level jet while winds at 500mb veer westerly at around 30-40 knots. Stronger mid/upper level winds will head east out of the Northern Plains with H5 winds of 50-60 knots and upper level winds approaching 90 knots.
Severe thunderstorms could develop with the above mentioned ingredients with large hail and damaging winds being the primary hazards. The threat for tornadoes looks somewhat lower, I would like to see more of a SSE surface wind, but they are forecast to be more SW which may tend to lower the potential for tornadoes. Stay tuned…
Highs Tomorrow will be in the 80s and 90s with 70s in far Northern Minnesota. It will be cooler especially along the North Shore of Lake Superior. Lows Tomorrow Night will be in the 60s and 70s. Winds will be out of the south, southwest or east at 10 to 20 mph.
*Thursday’s severe thunderstorm probability forecast. Much of the Northland remains in a 30% risk zone with even a hatched area now in Northcentral Minnesota, the hatched area means there could be significant severe weather events within 25 miles of a point. (Source, NWS/Storm Prediction Center)
*These following images are off the 15z SREF model from 7/17/13. This 1st map is the 24 hour calibrated severe weather forecast note the maxed out values over the Northland.
*Significant tornado values of 1-2 are still showing up in the North half of Minnesota for Thursday PM
*And this last map is the tornado ingredients forecast valid for Thursday PM – again pretty high values continue to show up over Northern MN. I’m a little skeptical on the tornado threat for Thursday, but there certainly could be severe t-storms and even some supercells.
Extended Forecast – Confidence: High.
Friday through Sunday (July 19th-21st)
This period is looking cooler with much less humidity. The drop in dew points will occur from NW-SE on Friday as a cold front exits the Northland. Could see a few showers or thunderstorms on Friday, but Saturday and Sunday are looking generally dry at this time. Highs will be in the 70s and 80s on Friday and in the 60s and 70s Saturday and Sunday. Lows Friday Night and Saturday Night will be in the 40s and 50s.
Long Range Forecast – Confidence: High.
Could see a few showers or thunderstorms at times through this period with near to above average temperatures forecast.
5 DAY FORECAST FOR DULUTH/SUPERIOR
.Tonight… Humid. Partly to mostly cloudy. Scattered showers and thunderstorms possible. Low 65 to 70. Wind west to southwest at 10 to 20 mph becoming east.
.Thursday… Humid. Scattered showers and thunderstorms possible. High 85 to 90 but cooler near Lake Superior. Wind east to southeast at 5 to 15 mph becoming southwest at 10 to 20 mph.
.Thursday Night… Showers and thunderstorms possible. Low 60 to 65. Wind southwest at 10 to 20 mph becoming west to northwest late.
.Friday… Partly sunny. Turning less humid. High 80 to 85.
.Friday Night… Partly cloudy. Low 50 to 55.
.Saturday… Partly sunny. High 70 to 75.
.Saturday Night… Mostly clear. Low 45 to 50.
.Sunday… Partly cloudy. High 70 to 75.
Normal temperatures for Today
Sunrise Thursday: 5:33 AM CDT
Sunset Thursday: 8:56 PM CDT